Re: [Xc3sprog-users] SPI programming - delayed reads

[Uwe B. <bo...@el...>]

>>>>> "Álvaro" == Álvaro Lopes <alv...@al...> writes:

    Álvaro> Uwe Bonnes wrote:
    >> Looking at the protocoll in S71296_05.pdf, I think you won't gain
    >> much. Polling in the 10 us timeframe required for the Byte
    >> programming time (TBP) is always slow if USB round trips are
    >> involved.
    >> 
    >> Combining AAI/ trigger Read software status/ read software status to
    >> one single USB transfer will probably always return "not ready" as
    >> the 10 us TBP wait time has not yet elapsed and so you have to go
    >> another USB round trip for the next poll cycle.
    >> 
    >> What about adding the hardware poll mechanism to the BSCAN-SPI core?

    Álvaro> That would add much complexity to the core, I'd prefer to avoid
    Álvaro> that (of course a specific bscan part can be provided).

    >> Or perhaps you add dummy SCK cycles with CE high to fullfill the
    >> "wait TBP" requirement? No need to poll then.

    Álvaro> This is indeed interesting. The only problem I see right now is
    Álvaro> that there seems not to be a way to figure out TCK frequency.

SCK frequency for the BSCAN SPI core is the TCK frequency. But we have only
control on the tck frequency of the FTDI...

    >>  Remember that every POLL needs at least 125 us USB round trip (to my
 ...

    Álvaro> I did implement with non-busy check, meaning no wait for tBP
    Álvaro> (works well for low speeds), and I can erase+program+verify in
    Álvaro> about 6 seconds (increasing the FTDI JTAG frequency to its
    Álvaro> maximum). Other approaches (except for TCK one, which adds about
    Álvaro> 2 seconds) are painfully slow.

    Álvaro> While doing so, I have found some bugs on read and verify which
    Álvaro> I'll address later on this mailing list.

    Álvaro> The current implementation is an exception to the rule, like
    Álvaro> AT45 parts. I wonder if it would be best to have a separate
    Álvaro> class, with override-able methods, and implement the generic
    Álvaro> case on base class, and have AT45 and SST derive from it and
    Álvaro> implement the specifics on their classes.

If you still need to load BSCAN-SPI, it's an exception to the rule. If
BSCAN-SPI isn't loaded, it's a seperate class, in my opinion. But at last,
it is your implementation...

Bye
-- 
Uwe Bonnes                bo...@el...

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------